Pathological investigation and viral antigen distribution of emerging African swine fever in Vietnam

FIGURE 1. Gross lesions in ASFV‐infected pigs in Vietnam, 2019 (1a–f). Marble‐like haemorrhage in the superficial inguinal lymph nodes, case 18 (a). Diffuse haemorrhage in the mesenteric lymph nodes, case 74 (b). Petechial haemorrhage on the renal capsule, renal cortex and diffuse haemorrhage in the renal pelvis, case 18 (c). Hyperaemic splenomegaly in relation to the size of the stomach. Gastrohepatic lymph nodes showed diffuse haemorrhage, case 59 (d). Ecchymoses of the epicardium with serosanguinous pericardial fluid, case 58 (e). Ecchymoses of the myocardium, case 58 (f) [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 2. Splenic tissue of an ASF‐infected pig, HE staining (1a–c). Mild splenic haemorrhage in case 18. The cells of red pulp are discernible, and a few lymphoid follicles are present (a). Moderate splenic haemorrhage in case 19. There are moderate increases of erythrocytes in the red pulp and fewer discernible lymphoid follicles (b). Severe splenic haemorrhage in case 57. The red pulp parenchyma is largely replaced by erythrocytes; there are noticeable necrotic tissues and less discernable lymphoid follicles (c). Hepatic tissue of ASF‐infected pig, HE staining (1d–f). Mild hepatic haemorrhage of case 58. There is a focus of haemorrhage (arrowhead) in zone 2 (d). Moderate haemorrhage in case 18. There are multifocal haemorrhages in several hepatic lobules (e). Severe haemorrhage in pig 20. There are generalized, diffuse and necrotizing haemorrhages in the hepatic parenchyma (f) [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 3. Tonsillar tissue of ASF‐infected pig, HE staining (2a–c). The tonsil of case 20 under low magnification does not show remarkable changes (a). In higher magnification, connective fibrous tissue shows enhanced appearance (b). Apoptotic cells in the diffuse lymphoid area are easily appreciated in this magnification (asterisk). The lymphoid follicle (F) contains very few apoptotic bodies (c) [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 4. HE staining of tissues from ASF‐infected pigs (3a–i). There is sinus haemorrhage in the lymph node tissue of case 58 (a). Interstitial pneumonia and an increased number of pulmonary intravascular macrophages are present in the lung tissue of case 58 (b). Three to four layers of mononuclear cell infiltrations in the meninges and perivascular cuffing are present in the cerebral tissue of case 20. The inset shows swollen endothelial cells and apoptotic bodies in the perivascular cuffing lesion (c). Epicardial and myocardial haemorrhage with infiltration of mononuclear cells is present in the heart tissue of case 18 (d). Multifocal haemorrhages are seen in the superficial and deep lamina propria in the gastric epithelial tissue of case 58 (e). Multifocal haemorrhages are present in the outer longitudinal muscularis layer in the small intestinal tissue of case 18 (f). The large intestinal tissue of case 58 shows multifocal haemorrhages in the deep lamina propria and dilated capillaries filled with erythrocytes in the submucosa layer with extensive oedema beneath (g). There is extensive haemorrhage in the pelvis region of the renal tissue in case 20 (h). Multifocal haemorrhages are…

FIGURE 5. Immunohistochemical staining detection of ASFV antigen in the pig tissues (a–l). Most of the ASFV‐positive cells are detected in necrotizing macrophages in the splenic tissue of case 57 (a). Many Kupffer cells and/or circulating macrophages are positive in the hepatic sinusoids of the liver tissue in case 20 (b). Arrowheads show hepatocytes with positive staining in the liver tissue of case 20 (c). M cells in the epithelial crypt of tonsil and mononuclear cells in the diffuse lymphoid area are positive in the tonsillar tissue of case 20 (d). Positive cells are present in the sinus of the lymph node tissue of case 58. Many of the positive cells are erythrocyte‐laden macrophages (e). Two pulmonary intravascular macrophages are positive in the lung tissue of case 58 (f). A few mononuclear cells in the cerebral meninges are positive in the cerebral tissue of case 20 (g). Positive cells are present in the perivascular cuffing in the cerebral tissue of case 20 (h). Many spindle‐shaped cells are positive in the epicardial haemorrhage in the cardiac tissue of case 18 (i). Within the haemorrhagic region of the renal pelvis, macrophage/mononuclear cells and many spindle‐shaped cells are…